The present study investigated the validity for Japanese students of a vulnerability model of social skills deficits proposed by Segrin (1996). According to the model, it was assumed that social skills deficits were not causes or consequences of depression, loneliness, and social anxiety. Rather, they constituted vulnerability factors, and it was the interaction of social skills deficits and negative life events that predicted the development of depression, loneliness, and social anxiety. Two hundred and fifty-three students recorded scales of social skills, depression, loneliness, and social anxiety three times at intervals of three months. Results indicated that the interaction of social skills deficits and negative life events predicted the development of depression, loneliness, and social anxiety significantly in some cases, but social skills deficits alone were also significant in their prediction. It was considered that the method of using a multiple regression analysis following Segrin (1996, 1999) would not be appropriate for proving the model. The validity of lumping depression, loneliness, and social anxiety together and applying them to the same model was discussed.